Portable turbulent flow comparison rheometer

ABSTRACT

The invention is a portable turbulent flow comparison rheometer for evaluation of fluids exhibiting drag-reducing properties. The device is capable of directly measuring and recording differences in flow rates produced by identical pressures between two fluids.

[4 1 Oct. 23, 1973 PORTABLE TURBULENT FLOW COMPARISON RHEOMETER 75Inventor: John C. Limpert, Baltimore, Md. Primary Examiner-RichardQueissel' Assistant Examiner-Joseph W. Roskos Attorney-11. S. Sciasciaet al.

represented by the Secretary of the Navy ABSTRACT The invention is aportable turbulent flow comparison rheometer for evaluation of fluidsexhibiting dragreducing properties. The device is capable of directly[52] U.S. Cl. 73/56 measuring and recording iff rences in flowrates-pro- G01 11/04 duced by identical pressures between two fluids.73/56, 55, 57

[51] Int. Cl.

[58] Field of Search.............................

9 Claims, 2 Drawing Figures References Cited UNITED STATES PATENTS L i58 n 66 6O 68 INVENTOR. JOHN C. LIMPERT FIG. I.

PATENTEDHCI 23 1975 SHEH 2 0F 2 INVENTOR. JOHN C. L/MPERT AGENT TTORNEYPORTABLE TURBULENT FLOW COMPARISON Rl-IEOMETER The invention describedherein may be manufactured and used by or for the Government of theUnited States of America for Governmental purposes without the paymentof any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Reduction of drag in turbulent fluid flow bythe addition of minute amounts of certain high molecular weight organicpolymers has received growing interest in recent years. Concurrently,there existed a need for a simple, rapid, and accurate means to measuredragreduction. The US. Pat. No. to Hoyt, 3,327,522, shows a recentattempt to produce such an instrument. The Hoyt instrument utilizesconstant velocity while measuring changes in pressure. The instantinvention, however, utilizes constant. pressure while measuring changesin velocity. The instant invention has the further advantages that it isportable, and gives a direct.

comparison between a standard and a, test liquid, whereas the Hoytdevice is not portable and requires two separate measurements. It mustbe noted that the US, Pat. No. to Priest, 1,529,811, at first glance,appears structurally similar to the instant invention. The instantinvention is a turbulent flow rheometer, whereas Priest discloses alaminer flow instrument. Laminer flow instruments deal only withfunctions and used only to measure Newtonian fluids. Specifically, thePriest instrument is a viscosity measuring device. Structurally, thepistons of Priest are not in fluid tight contact with the cylinderwalls, as in the instant invention, and, in fact, the Priest invention,depends on such clearance to be operative. Viscosity measuring devicesrequiring laminer flow have been in existence for more than 400 years.Only recently have attempts been made to produce a turbulent flowrheometer to evaluate drag-reduction.

SUMMARY OF THE INVENTION The general purpose of the portable turbulentflow comparison rheometer is to provide a device to correctly measureand record differences in flow rate, produced by identical pressuresbetween two fluids; said device being portable and requiring no externalpower.

OBJECTS OF THE INVENTION provide a portable, simple to operate rheometerwhich requires no external power source. v

Still another object of the instant invention is to produce an apparatuswith good precision that is sensitive to low concentrations of highmolecular weight organic polymers.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the portable turbulentflow comparison rheometer in operation;

FIG. 2 shows the specific recording device and typical data obtained inFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT with that of the service fluidcontaining the dragreduction polymer leading to the formula PercentDrag-Reduction t, t,,/t, X 100 (l) where t, wall shear stress of theservice fluid;

t, wall shear stress of the service fluid plus polymer. Since the wallshear stress is directly proportional to the pressure drop, AP, equation(1) can also be written Percent Drag-Reduction AP, AP,,/AP, X 100 (2)Equations (1) and (2) represent the concept of comparing two fluidshaving different rheological properties. This is done by makingsuccessive measurements of the pressure drop between two points along acapillary tube under turbulent flow conditions. This requires drillingtwo holes into the capillary tube and attaching a differential pressuretransducer. Signals from the transducer are amplified for recordingpurposes. This is a method disclosed in the US. Pat. No. to Hoyt,

The concept of the comparison rheometer involves making simultaneousmeasurements of the fluids with and without the polymer additive,recording the difference, and relating this difference directly to theamount of drag-reduction.

With continued reference to the drawing, FIG. 1 shows a pair ofcommercially available glass syringes and 57. The syringes compriseplungers 56 and 54, shafts 58 and 60, cylinders 66 and 68, and syringeneedles 76 and 74, respectively. One syringe for example, 55, is filledwith a control fluid 63, usually water, the other syringe is filled witha test fluid'65, usually water plus a'drag-reducing agent. After the airis expelled, each needle 76 and 74-, is capped with astopper 78 and 80,respectively. The'syrin'ges 55 and 57 are then inserted into theirrespective holders 72 and 70. The load unit 31 is then connected withthe'plungers 56 and 54. The loadunit 31 comprises weight rod 14connected to weight container 88, the weight rod being connectedby pin32 to the T-head 10, which connects through pins 34 and 30 to load rods12 and 16, respectively. load rods 12 and 16 are connected by pins 48and 46 at their lower ends to sleevemembers 42 and 44, respectively.Sleeve members 42 and 44 slide vertical direction freely with respect tosupport bar 40. Support bar 40 and holders 70 and 72 are all rigidlyattached to back plate 8. It is noted that weight container 88 maycontain various desired loads corresponding to desired pressures thatthe fluids may be subjected to. Push plates 50 and 52, connected to thelower ends of-sleeve members 42 and 44, rest upon plun'gers 56 and 54,respectively. Weight rod 14'is free to slide in the vertical directionthrough support bar 40 via guide 15. Push plates 50 and 52 are placed incontact with plungers 56 and 54, respectively.

The recording device 6 also includes the T-head 10 of the load unit 31,and holder 20 connected by pin 28 to T-head 10. The holder 20 holds awriting instrument 22 via thumbscrew 24. The holder 20 is biased towardrecording paper 26 by biasing means 18. Biasing means 18 may be anyresilient means and is connected to holder 20 and T-head 10 byprojections 38 and 36. The writing instrument 22 is placed in contactwith the recording paper 26. The hinged trigger 82 is then depressedwhich simultaneously pushes both stoppers 78 and 80 from the end of eachneedle 76 and 74 into the cups 86 and 84. Cups 86 and 84 are attached toback plate 8 by supports 85 and 87, respectively. The load of load unit31 is now equally divided by the T-head l and applied to both syringeplungers 56 and 54 by the load rods 12 and 16 inside the sleeve members42 and 44. The entire load unit 31 descends as each syringe 55 and 57exhausts to its cup, 86 and 84, respectively. If

the flow properties of the fluids differ, one syringe will empty morerapidly than the other causing the T-head to tilt as it descends thuscausing the writing instrument 22 to trace a diagonal line upon therecording paper 26. The diagonal line will continue until the piston 62or 64 of the faster running syringe bottoms out. The control syringewill now continue until its piston bottoms out while the writinginstrument traces an are back to the neutral position. The weightcontainer 88 is then removed with the writing instrument 22 still incontact with the recording paper 26. The mechanism is gently raised andlowered by hand, touching only the weight rod 14. A straight verticalstroke line should be traced, indicating no stray friction in themechanical components. The writing instrument 22 is now lifted and themechanism raised and held in its highest position again. The cups areemptied and the stoppers 78 and 80 retrieved. This completes one-half ofthe test. The syringes are now extracted from their respective holdersandfilled for the second half of the test, this time with the controlfluid in the syringe that previously contained the test fluid. Repeatthe same procedure. This time, the diagonal trace will fall on theopposite side of the vertical stroke line.

With reference to FIG. 2, while there is no significant friction in themechanical components, there are slight differences in the slidingcharacteristics between the syringes. This effect is manifested in thisdevice by what might be termed a machine constant which in FIG. 2 areangles LOL' positive and the angle TOT negative. The error due tonon-identical friction inthe mechanical components is overcome by makingtwo runs and switching the control fluid to alternative syringes foreach of the two test runs, the machine'constant is made to cancel andthe actual trace angle LOT equals the theoretical angle L'OT'. Themagnitude of angle LOT is directly proportional to the amount of dragreduction.

In the following explanation only one side of the diagram need beconsidered. Line OP defines the stroke direction. Its length isproportional to the time required for the control syringe to empty. Thistime may be used as a reference and will be constant unless there arealterations in applied weight, temperature, or needledimensions. Line OPwould be the trace if both syringes contained the same fluid. When atest fluid is compared with water, the test trace proceeds from O to T.Point T occurs when the test fluid syringe is emptied and its piston hasbottomed out. The writing instrument now goes along the return line ATPto point P where the water syringe is now empty. The return line ATP isa circumference whose radius is the hypotenuse of the T-head and iscentered on the test fluid syringe center line. The time taken for thetest fluid to discharge from its syringe may be determined as follows:the theoretical angle LOT' is constructed by measuring the actual angleLOT and placing it so that its bisector is line OP. The radius r iscentered on the water syringe center line so that its circumferenceintersects ATP..at T, which is the end point of the corrected testtrace, and OP at X. The test fluid discharge time equals the linearratio OX/OP times the constant discharge time when both syringes arefilled with water. The flow rate then may be determined from this testtime and volume discharged. Geometry of the rheometer components,weight, and reference time are known. If densities, viscosities, andsyringe needle cross-section areas are also known, the Reynolds numbercan also be calcualted. Angle TOP is a function of fluid drag-reductionsince identical conditions have produced different flow rates. Otherflow rates may be obtained by varying weight and/or needle dimensions.

It is understood that the invention is not limited to the exact detailsof construction shown and described for obvious modifications will occurto persons skilled in the art. It is therefore to be understoodthat'within the scope of the appended claims, the invention may bepracticed otherwise than as specifically described.

What is claimed is:

1. A portable turbulent flow comparison rheometer for drag-reductioncomparison of two fluids, which comprises:

first and second fluid containing means for holding said fluids to .becompared, said containing means having an orificial passage to allow thefluid to escape when pressure is exerted on said fluids; pressureexerting means connected to said first and second fluid containing meansto simultaneously apply equal and constant pressure to each fluid tocause turbulent flow through the orificial passage and I recording meansintegral with said pressure exerting means to record the emptying of thefirst and second fluid containing means with respect to each other andthereby compare the two fluids dragreduction characteristics.

2. A device as in claim 1 wherein said pressure exerting means is influid tight relationship to said first and second fluid containingmeans. i

3. A device as in claim 2 wherein said pressure exerting means includesa T-bar operativ ely connected at the symmetrical ends of the cross barthereof to saidfirst and second pressure exerting means, said recordingmeans being integral with the end of the stem of said T-bar. I I

4. A device as in claim 3 wherein said pressure exerting means furtherincludes load means pivotly connected to said T-bar to rotate about theconnection of said load means to said T-bar if one fluid is expelledfrom either of the containing means faster than the other.

5. A device as in claim 4 wherein said first and second fluid containingmeans are syringes.

6. A device as in claim 3, wherein 'said recording means includes a penattached to said T-bar so as 'to scribe an angle with the vertical whichis a measure of the tilt of the T-bar, comprising:

a vertical surface; and

a means to bias said pen against said vertical surface to record thedifferential motion between said first and second pressure exertingmeans during the descent of the T-bar.

7. A portable turbulent flow comparison rheometer as in claim 1,wherein;

said pressure exerting means includes a weight which causes the pressureexerting means to apply equal and constant pressure to each fluid toforce the fluids out of their respective fluid containing means.

8. A device suspended by a support bar as in claim 1, wherein;

said pressure exerting means comprises;

a first and second piston;

a first and second push plate engaging said first and second pistonrespectively;

a first and second sleeve member slidingly engaged with said support barand rigidly attached and extending vertically from said respective firstand second push plates;

a first and second load rod substantially within said placing a secondliquid in a second fluid containing means;

placing a first and second pressure exerting means in fluid tightrelationship with said first and second fluid containing meansrespectively;

releasing a weight to apply a constant and equal force through a linkageto the pressure exerting means;

allowing the pressure exerting means to move with respect to said fluidcontaining means and exert a constant pressure on said fluid;

allowing the first and second liquids to pass by turbulent flow throughan orifice leading to a tube from each of the first and second fluidcontaining means;

producing a line on a vertical surface which is at an angle with thevertical wherein said angle is a measure of the relative speed ofturbulent flow through the orifice of said first and second fluidcontaining means respectively;

raising the weight to its initial position;

completely exchanging the fluids by placing said first liquid in saidsecond fluid containing means and placing said second liquid in saidfirst liquid containing means; repeating the above steps to produce aline opposite the vertical from the previously recorded line so that theangle between the two lines is an indicia of the relative turbulent flowcharacteristics of the compared liquids without error due to lack ofprecise identity of thefirst and second mechanisms.

1. A portable turbulent flow comparison rheometer for dragreductioncomparison of two fluids, which comprises: first and second fluidcontaining means for holding said fluids to be compared, said containingmeans having an orificial passage to allow the fluid to escape whenpressure is exerted on said fluids; pressure exerting means connected tosaid first and second fluid containing means to simultaneously applyequal and constant pressure to each fluid to cause turbulent flowthrough the orificial passage and recording means integral with saidpressure exerting means to record the emptying of the first and secondfluid containing means with respect to each other and thereby comparethe two fluids'' drag-reduction characteristics.
 2. A device as in claim1 wherein said pressure exerting means is in fluid tight relationship tosaid first and second fluid containing means.
 3. A device as in claim 2wherein said pressure exerting means includes a T-bar operativelyconnected at the symmetrical ends of the cross bar thereof to said firstand second pressure exerting means, said recording means being integralwith the end of the stem of said T-bar.
 4. A device as in claim 3wherein said pressure exerting means further includes load means pivotlyconnected to said T-bar to rotate about the connection of said loadmeans to said T-bar if one fluid is expelled from either of thecontaining means faster than the other.
 5. A device as in claim 4wherein said first and second fluid containing means are syringes.
 6. Adevice as in claim 3, wherein said recording means includes a penattached to said T-bar so as to scribe an angle with the vertical whichis a measure of the tilt of the T-bar, comprising: a vertical surface;and a means to bias said pen against said vertical surface to record thedifferential motion between said first and second pressure exertingmeans during the descent of the T-bar.
 7. A portable turbulent flowcomparison rheometer as in claim 1, wherein; said pressure exertingmeans includes a weight which causes the pressure exerting means toapply equal and constant pressure to each fluid to force the fluids outof their respective fluid containing means.
 8. A device suspended by asupport bar as in claim 1, wherein; said pressure exerting meanscomprises; a first and second piston; a first and second push plateengaging said first and second piston respectively; a first and secondsleeve member slidingly engaged with said support bar and rigidlyattached and extending vertically from said respective first and secondpush plates; a first and second load rod substantially within saidrespective first and second sleeve members and connected to a T-bar ontheir upper ends and attached to said respective first and second pushplates below the point of sliding engagement between said first andsecond sleeve members and said support bar.
 9. A method of comparing theturbulent, non-viscous flow characteristics of two liquids comprising:placing a first liquid in a first fluid containing means; placing asecond liquid in a second fluid containing means; placing a first andsecond pressure exerting means in fluid tight relationship with saidfirst and second fluid containing means respectively; releasing a weightto apply a constant and equal force through a linkage to the pressureexerting means; allowing the pressure exerting means to move withrespect to said fluid containing means and exert a constant pressure onsaid fluid; allowing the first and second liquids to pass by turbulentflow through an orifice leading to a tube from each of the first andsecond fluid containing means; producing a line on a vertical surfacewhich is at an angle with the vertical wherein said angle is a measureof the relative speed of turbulent flow tHrough the orifice of saidfirst and second fluid containing means respectively; raising the weightto its initial position; completely exchanging the fluids by placingsaid first liquid in said second fluid containing means and placing saidsecond liquid in said first liquid containing means; repeating the abovesteps to produce a line opposite the vertical from the previouslyrecorded line so that the angle between the two lines is an indicia ofthe relative turbulent flow characteristics of the compared liquidswithout error due to lack of precise identity of the first and secondmechanisms.